Transmission method, reception method, transmission apparatus, and reception apparatus

ABSTRACT

A transmission method includes: generating one or more transfer frames that each store one or more streams used for content transfer; and transmitting the one or more generated frames through broadcast, each of the one or more streams storing one or more second transfer units, each of the one or more second transfer units storing one or more first transfer units, and each of the one or more first transfer units storing one or more Internet Protocol (IP) packets. In at least one stream among the one or more streams, each of the first transfer units positioned at a head contains reference clock information indicating time used for reproduction of the content.

BACKGROUND 1. Technical Field

The present disclosure relates to a transmission method and the like fortransferring content by using IP (Internet Protocol) packets throughbroadcast.

2. Description of the Related Art

An MMT scheme (refer to NPTL 1) is a multiplexing scheme formultiplexing and packetizing content such as video and audio and fortransmitting the content through one or more transfer channels such asbroadcast and broadband. When the MMT scheme is applied to broadcastingsystems, reference clock information of a transmission apparatus istransmitted to a reception apparatus, and the reception apparatusgenerates a system clock in the reception apparatus based on thereference clock information.

CITATION LIST Non-Patent Literature

NPTL 1: Information technology-High efficiency coding and media deliveryin heterogeneous environments-Part1: MPEG media transport (MMT), ISO/IECFDIS 23008-1

SUMMARY

In one general aspect, the techniques disclosed here feature atransmission method including: generating one or more transfer framesthat each store one or more streams used for content transfer; andtransmitting the one or more generated frames through broadcast, each ofthe one or more streams storing one or more second transfer units, eachof the one or more second transfer units storing one or more firsttransfer units, each of the one or more first transfer units storing oneor more Internet Protocol (IP) packets. In at least one stream among theone or more streams, each of the first transfer units positioned at ahead contains reference clock information indicating time used forreproduction of the content.

The transmission method and the like according to one aspect of thepresent disclosure may reduce processes for acquiring the referenceclock information by a reception apparatus.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a protocol stack for performingtransfer using an MMT scheme and an advanced BS transfer scheme;

FIG. 2 is a diagram illustrating data structure of a TLV packet;

FIG. 3 is a block diagram illustrating a basic configuration of areception apparatus;

FIG. 4 is a block diagram illustrating a functional configuration of thereception apparatus when reference clock information is stored in anextension field of an MMT packet header;

FIG. 5 is a diagram illustrating an acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the extension field of the MMTpacket header;

FIG. 6 is a block diagram illustrating the functional configuration ofthe reception apparatus when the reference clock information is storedin control information;

FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the control information;

FIG. 8 is a block diagram illustrating the configuration of thereception apparatus when the reference clock information is stored inthe TLV packet;

FIG. 9 is a diagram illustrating an example in which a long-format NTPis stored in the TLV packet;

FIG. 10 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the TLV packet;

FIG. 11 is a diagram illustrating structure in which the reference clockinformation is appended immediately before an IP packet header;

FIG. 12 is a diagram illustrating structure in which the reference clockinformation is appended immediately before the TLV packet;

FIG. 13 is a diagram illustrating structure of a transfer slot;

FIG. 14 is a diagram illustrating structure of a slot header of thetransfer slot;

FIG. 15 is a diagram illustrating an example in which a flag is storedin an undefined area of the slot header;

FIG. 16 is a diagram illustrating structure of TMCC control informationunder a transfer scheme of an advanced broadband satellite digitalbroadcast;

FIG. 17 is a diagram illustrating stream classification/relative streaminformation of the TMCC control information;

FIG. 18 is a diagram illustrating an example in which the referenceclock information is stored in an undefined field of the slot header;

FIG. 19 is a block diagram illustrating the functional configuration ofthe reception apparatus when information indicating that the referenceclock information is contained within the slot header is stored in TMCCcontrol information;

FIG. 20 is a diagram illustrating the acquisition flow of the referenceclock information when the information indicating that the referenceclock information is contained in the slot header is stored in the TMCCcontrol information;

FIG. 21 is a diagram illustrating a flow of extracting a bit string at aspecific position from the IP packet or compressed IP packet;

FIG. 22 is a block diagram illustrating a functional configuration of atransmission apparatus; and

FIG. 23 is a diagram illustrating an operation flow of the transmissionapparatus.

DETAILED DESCRIPTION (Underlying Knowledge Forming Basis of the PresentDisclosure)

The present disclosure relates to a method and apparatus in which areception apparatus receives reference clock information transmittedfrom a transmission apparatus and generates (reproduces) a referenceclock in a hybrid delivery system using an MMT (MPEG Media Transport)scheme which is under standardization by MPEG (Moving Picture ExpertGroup).

The MMT scheme is a multiplexing scheme for multiplexing and packetizingvideo and audio to transmit the video and audio via one or more transferchannels, such as broadcast and broadbands.

When the MMT scheme is applied to a broadcasting system, the referenceclock of the transmission apparatus is synchronized with an NTP (NetworkTime Protocol) prescribed by IETF RFC 5905, and based on the referenceclock, a time stamp such as PTS (Presentation Time Stamp) and DTS(Decode Time Stamp) is added to a medium. Furthermore, the transmissionapparatus transmits the reference clock information to the receptionapparatus, and the reception apparatus generates the reference clock(hereinafter referred to as a system clock) in the reception apparatusbased on the reference clock information.

In the broadcasting system, a 64-bit long-format NTP capable ofindicating absolute time is preferably used as the reference clockinformation. However, although the conventional MMT scheme prescribesstoring a 32-bit short-format NTP in an MMT packet header andtransferring the 32-bit short-format NTP, the conventional MMT schemedoes not prescribe transferring the long-format NTP, and it is difficultfor a receiver apparatus to acquire high-precision reference clockinformation.

In contrast, control information, such as a message, a table, and adescriptor, is defined using the long-format NTP. It is possible toappend the MMT packet header to the control information for transfer. AnMMT packet, which is the control information to which the MMT packetheader is appended, is stored in an IP packet, and is transferredthrough a broadcast transfer channel or a broadband transfer channel.

When the MMT packet is transferred using an advanced BS transfer schemeprescribed by the ARIB standard (transfer scheme of an advancedbroadband satellite digital broadcast), after encapsulation of the MMTpacket into the IP packet and encapsulation of the IP packet into a TLV(Type Length Value) packet, the MMT packet is stored in a transfer slotprescribed by the advanced BS transfer scheme.

However, when the transmission apparatus stores the reference clockinformation in an MMT packet layer, in order to obtain the referenceclock information, the reception apparatus extracts the TLV packet fromthe transfer slot, extracts the IP packet from the TLV packet, extractsthe MMT packet from the IP packet, and further extracts the referenceclock information from the header or a payload of the MMT packet.Therefore, the reception apparatus involves many processes for acquiringthe reference clock information, and needs longer time until theacquisition.

Also, processes in layers equal to or higher than an IP layer aresoftware processes. Accordingly, when the reference clock information isstored in the MMT packet, the reference clock information is extractedand reproduced by a software program. Therefore, the reference clockinformation to be acquired may contain jitter, by throughput of a CPU,interruption from and priority of other software programs, and the like.

Therefore, a transmission method according to one aspect of the presentdisclosure includes: generating one or more transfer frames that eachstore one or more streams used for content transfer; and transmittingthe one or more generated frames through broadcast, each of the one ormore streams storing one or more second transfer units, each of the oneor more second transfer units storing one or more first transfer units,each of the one or more first transfer units storing one or moreInternet Protocol (IP) packets. In at least one stream among the one ormore streams, each of the first transfer units positioned at a headcontains reference clock information indicating time used forreproduction of the content.

Thus, by containing the reference clock information in the TLV packetpositioned at a head within a head slot in one or more streams containedin the transfer slot, the reception apparatus may specify a position ofthe reference clock information of the at least one stream in advance.Therefore, the reception apparatus may reduce (simplify) processes foracquiring the reference clock information of the one or more streams.Here, an example of the first transfer unit is a TLV packet. An exampleof the second transfer unit is a slot, and an example of the transferframe is a transfer slot.

In addition, by containing the reference clock information in the TLVpacket positioned at a head within the slot positioned at a head in eachof the streams contained in the transfer slot, the reception apparatusmay specify the position of the reference clock information on each ofthe plurality of streams in advance. Therefore, the reception apparatusmay reduce (simplify) the processes for acquiring the reference clockinformation on each of the plurality of streams.

In addition, each of the first transfer units may be a variable-lengthtransfer unit, and each of the second transfer units may be afixed-length transfer unit.

In addition, each of the first transfer units positioned at a head mayinclude an IP packet that does not undergo header compressionprocessing.

Thus, by the transmission apparatus prescribing presence of headercompression of the IP packets, the reception apparatus may specify theposition of the reference clock information in more detail. Therefore,the reception apparatus may simplify the process for acquiring thereference clock information.

In addition, each of the first transfer units may be a Type Length Value(TLV) packet, each of the second transfer units may be a slot under thetransfer scheme of the advanced broadband satellite digital broadcast,and the frame may be a transfer slot under the transfer scheme of theadvanced broadband satellite digital broadcast.

In addition, the reference clock information may be a Network TimeProtocol (NTP).

In addition, the one or more frames may be transmitted in apredetermined transmission cycle.

A reception method according to one aspect of the present disclosureincludes: receiving one or more frames through broadcast; extractingreference clock information from at least one frame among the one ormore received frames; and generating a clock used for reproduction ofcontent by using the extracted reference clock information, each of theone or more frames containing one or more second transfer units, each ofthe one or more second transfer units containing one or more firsttransfer units, and each of the one or more first transfer unitscontaining one or more Internet Protocol (IP) packets.

A transmission apparatus according to one aspect of the presentdisclosure includes: generation circuitry which, in operation, generatesone or more frames used for content transfer; and transmission circuitrywhich, in operation, transmits the one or more generated frames throughbroadcast, each of the one or more streams storing one or more secondtransfer units, each of the one or more second transfer units storingone or more first transfer units, and each of the one or more firsttransfer units storing one or more Internet Protocol (IP) packets. In atleast one stream among the one or more streams, each of the firsttransfer units positioned at a head contains reference clock informationindicating time used for reproduction of the content.

A reception apparatus according to one aspect of the present disclosureincludes: reception circuitry which, in operation, receives one or moreframes; extraction circuitry which, in operation, extracts referenceclock information from at least one frame among the one or more receivedframes; and a generator that generates a clock used for reproduction ofthe content by using the extracted reference clock information, each ofthe one or more frames containing one or more second transfer units,each of the one or more second transfer units containing one or morefirst transfer units, and each of the one or more first transfer unitscontaining one or more Internet Protocol (IP) packets.

Note that these general or specific aspects may be implemented using asystem, an apparatus, a method, an integrated circuit, a computerprogram, or a computer-readable recording medium such as a CD-ROM. Also,these general or specific aspects may be implemented using an arbitrarycombination of a system, an apparatus, a method, an integrated circuit,a computer program, and a recording medium.

First Exemplary Embodiment [Basic Configuration of an MMT Scheme]

First, a basic configuration of an MMT scheme will be described. FIG. 1illustrates a protocol stack diagram for performing transfer using theMMT scheme and an advanced BS transfer scheme.

Under the MMT scheme, information such as video and audio is stored in aplurality of MPUs (Media Presentation Units) and a plurality of MFUs(Media Fragment Units), and an MMT packet header is added forMMT-packetization.

Meanwhile, under the MMT scheme, the MMT packet header is also added tocontrol information such as an MMT message for MMT-packetization. TheMMT packet header is provided with a field that stores a 32-bitshort-format NTP, and this field may be used for QoS control ofcommunication networks, etc.

MMT-packetized data is encapsulated into an IP packet having a UDPheader or IP header. At this time, in the IP header or UDP header, whena set of packets with an identical source IP address, destination IPaddress, source port number, destination port number, and protocolclassification is an IP data flow, headers of a plurality of IP packetscontained in one IP data flow are redundant. Therefore, headercompression of some IP packets is performed in one IP data flow.

Next, a TLV packet will be described in detail. FIG. 2 is a diagramillustrating data structure of the TLV packet.

As illustrated in FIG. 2, an IPv4 packet, IPv6 packet, compressed IPpacket, NULL packet, and transfer control signal are stored in the TLVpacket. These pieces of information are identified using an 8-bit datatype. Examples of the transfer control signal include an AMT (AddressMap Table) and NIT (Network Information Table). Also, the TLV packetindicates a data length (byte unit) using a 16-bit field, and a value ofdata is stored thereafter. Since there is 1-byte header informationbefore the data type (not illustrated in FIG. 2), the TLV packet has aheader area of 4 bytes in total.

The TLV packet is mapped to a transfer slot under the advanced BStransfer scheme. Pointer/slot information that indicates a head positionof a first packet and a tail position of a last packet which arecontained in every slot are stored in TMCC (Transmission andMultiplexing Configuration Control) control information.

Next, a configuration of a reception apparatus that receives the MMTpacket transferred by using the advanced BS transfer scheme will bedescribed. FIG. 3 is a block diagram illustrating the basicconfiguration of the reception apparatus. Note that the configuration ofthe reception apparatus of FIG. 3 is simplified. More specificconfiguration will be individually described later according to a mannerin which reference clock information is stored.

Reception apparatus 20 includes receiver 10, decoder 11, TLVdemultiplexer (DEMUX) 12, IP demultiplexer (DEMUX) 13, and MMTdemultiplexer (DEMUX) 14.

Receiver 10 receives transfer channel coded data.

Decoder 11 decodes the transfer channel coded data received by receiver10, applies error correction and the like, and extracts a TMCC controlsignal and TLV data. The TLV data extracted by decoder 11 undergoesDEMUX processing by TLV demultiplexer 12.

The DEMUX process performed by TLV demultiplexer 12 differs according tothe data type. For example, when the data type is a compressed IPpacket, TLV demultiplexer 12 performs processes such as decompressingthe compressed header and passing the header to an IP layer.

IP demultiplexer 13 performs processes such as header analysis of the IPpacket or UDP packet, and extracts the MMT packet from each IP dataflow.

MMT demultiplexer 14 performs a filtering process (MMT packet filtering)based on a packet ID stored in the MMT packet header.

[Method for Storing the Reference Clock Information in the MMT Packet]

Under the MMT scheme described with reference to FIG. 1 to FIG. 3described above, although the 32-bit short-format NTP may be stored inthe MMT packet header and transferred, there exists no method fortransferring a long-format NTP.

Hereinafter, a method for storing the reference clock information in theMMT packet will be described. First, the method for storing thereference clock information within the MMT packet will be described.

When control information that defines a descriptor, a table, or amessage for storing the reference clock information is stored in the MMTpacket, the descriptor indicating the reference clock information and anidentifier indicating the table or message are indicated within thecontrol information. Then, the control information is stored in the MMTpacket by the transmission apparatus.

This allows reception apparatus 20 to identify the reference clockinformation based on the identifier. Note that the reference clockinformation may be stored in the MMT packet by using existingdescriptors (for example, CRI_descriptor( ), etc.).

Next, a method for storing the reference clock information in the MMTpacket header will be described.

For example, there is a method for storing the reference clockinformation by using a header_extension field (hereinafter referred toas an extension field). The extension field becomes effective when anextension_flag of the MMT packet header is set to “1”.

The reference clock information is stored in the extension field throughstorage, in the extension field, of an extension field type indicatingdata classification of data to be stored in the extension field, andthrough storage of information indicating the reference clockinformation (for example, a 64-bit long-format NTP) in the extensionfield type.

When the header_extension_flag of the MMT packet header is ‘1’,reception apparatus 20 references the extension field of the MMT packet.When the extension field type indicates the reference clock information,reception apparatus 20 extracts the reference clock information andreproduces a clock.

Note that the reference clock information may be stored in an existingheader field. In addition, when there is an unused field or when thereis a field unnecessary for broadcast, the reference clock informationmay be stored in these fields.

In addition, the reference clock information may be stored by using theexisting field and the extension field together. For example, theexisting 32-bit short-format NTP field and the extension field may beused together.

In the reference clock information, in order to maintain compatibilitywith the existing field, of the 64-bit long-format NTP, only a 32-bitsection corresponding to a short-format format may be stored in theexisting field, and remaining 32 bits may be stored in the extensionfield.

Here, the reference clock information is, for example, time when a headbit of the MMT packet in which the reference clock information is storedpasses a predetermined position (for example, when the head bit isoutput from a specific component of a transmission apparatus). However,the reference clock information may be time when a bit of anotherposition passes the predetermined position.

When the reference clock information is stored in the MMT packet as thecontrol information, the MMT packet containing the control informationis transmitted at predetermined transmission intervals.

When the reference clock information is stored in the extension field ofthe MMT packet, the reference clock information is stored in thepredetermined extension field of the MMT packet header. Specifically,for example, at least one or more pieces of the reference clockinformation are stored in the header extension field of the MMT packetat intervals of 100 ms.

Note that, when the reference clock information is stored in the MMTpacket, the packet ID of the MMT packet that stores the reference clockinformation is stored in program information. Reception apparatus 20analyzes the program information and acquires the MMT packet in whichthe reference clock information is stored. At this time, the packet IDof the MMT packet in which the reference clock information is stored maybe prescribed in advance as a fixed value. This allows receptionapparatus 20 to acquire the reference clock information withoutanalyzing the program information.

[Operation Flow when the Reference Clock Information is Stored in theMMT Packet]

Next, an operation flow when the reference clock information is storedin the MMT packet (acquisition flow of the reference clock information)will be described.

First, the following describes the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader. FIG. 4 is a block diagram illustrating a functionalconfiguration of reception apparatus 20 when the reference clockinformation is stored in the extension field of the MMT packet header.FIG. 5 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader.

In FIG. 4, when the reference clock information is stored in theextension field of the MMT packet header, MMT demultiplexer 14 includesreference clock information extractor 15 (an example of an extractor),and reference clock generator 16 (an example of a generator) is provideddownstream of MMT demultiplexer 14.

In the flow of FIG. 5, decoder 11 of reception apparatus 20 decodes thetransfer channel coded data received by receiver 10 (S101), and extractsthe TLV packet from the transfer slot (S102).

Next, TLV demultiplexer 12 performs DEMUX on the extracted TLV packet toextract the IP packet (S103). At this time, the header of the compressedIP packet is reproduced.

Next, IP demultiplexer 13 performs DEMUX on the IP packet, acquires thespecified IP data flow, and extracts the MMT packet (S104).

Next, MMT demultiplexer 14 analyzes the header of the MMT packet, anddetermines whether the extension field is used and whether the referenceclock information is in the extension field (S106). When there is noreference clock information in the extension field (No in S106), theprocess ends.

On the other hand, when the determination is made that the referenceclock information is in the extension field (Yes in S106), referenceclock information extractor 15 extracts the reference clock informationfrom the extension field (S107). Then, reference clock generator 16generates the system clock based on the extracted reference clockinformation (S108). The system clock is, in other words, a clock forreproducing content.

Next, the acquisition flow of the reference clock information byreception apparatus 20 when the reference clock information is stored inthe control information will be described. FIG. 6 is a block diagramillustrating the functional configuration of reception apparatus 20 whenthe reference clock information is stored in the control information.FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the control information.

As illustrated in FIG. 6, when the reference clock information is storedin the control information, reference clock information extractor 15 isdisposed downstream of MMT demultiplexer 14.

In the flow of FIG. 7, the processes of step S111 to step S114 areidentical to the flow of step S101 to step S104 described in FIG. 5.

Subsequent to step S114, MMT demultiplexer 14 acquires the packet ID ofthe packet containing the reference clock information from the programinformation (S115), and acquires the MMT packet of the packet ID (S116).Subsequently, reference clock information extractor 15 extracts thereference clock information from the control signal contained in theextracted MMT packet (S117), and reference clock generator 16 generatesthe system clock based on the extracted reference clock information(S118).

[Method for Storing the Reference Clock Information in the TLV Packet]

As described in FIG. 5 and FIG. 7, when the reference clock informationis stored in the MMT packet, in order to obtain the reference clockinformation, reception apparatus 20 extracts the TLV packet from thetransfer slot and extracts the IP packet from the TLV packet.Furthermore, reception apparatus 20 extracts the MMT packet from the IPpacket, and further extracts the reference clock information from theheader or a payload of the MMT packet. Thus, when the reference clockinformation is stored in the MMT packet, reception apparatus 20 has manyprocesses for acquiring the reference clock information, and longer timeis required until the acquisition, which need to be addressed.

Therefore, a method will be described for implementing a process ofadding a time stamp to a medium, such as video and audio, based on thereference clock, and a process of transferring the medium by using theMMT scheme, and for implementing transfer of the reference clockinformation by using a lower layer, lower protocol, or lowermultiplexing scheme than the MMT layer.

First, a method for storing the reference clock information in the TLVpacket for transfer will be described. FIG. 8 is a block diagramillustrating the configuration of reception apparatus 20 when thereference clock information is stored in the TLV packet.

Reception apparatus 20 illustrated in FIG. 8 differs from receptionapparatus 20 of FIG. 4 and FIG. 6 in placement of reference clockinformation extractor 15 and reference clock generator 16. In addition,synchronizer 17 and decoding presenter 18 are also illustrated in FIG.8.

The TLV packet includes the 8-bit data type, 16-bit data length, and8*N-bit data, as illustrated in aforementioned FIG. 2. In addition,1-byte header which is not illustrated in FIG. 2 exists before the datatype, as described above. Here, the data type is specificallyprescribed, for example, as 0x01: IPv4 packet, 0x03: header-compressedIP packet, etc.

In order to store new data in the TLV packet, an undefined area of thedata type is used to prescribe the data type. In order to indicate thatthe reference clock information is stored in the TLV packet, the datatype describes that the data is reference clock information.

Note that the data type may be prescribed for each kind of the referenceclock. For example, the data types that indicate the short-format NTP,long-format NTP, and PCR (Program Clock Reference) may be prescribedindividually. FIG. 9 is a diagram illustrating an example in which thelong-format NTP is stored in the TLV packet. The long-format NTP isstored in a data field.

In this case, reference clock information extractor 15 analyzes the datatype of TLV packet. When the reference clock information is stored,reference clock information extractor 15 analyzes the data length, andextracts the reference clock information from the data field.

Here, when the data length is uniquely determined by the data type,reference clock information extractor 15 may acquire the reference clockinformation without analyzing a data length field. For example, when thedata type indicates a 64-bit long format NTP, reference clockinformation extractor 15 may extract a section from 4 bytes+first bit to4 bytes+64-th bit. Also, reference clock information extractor 15 mayextract a desired bit from 64-bit data.

Next, the operation flow of reception apparatus 20 when the referenceclock information is stored in the TLV packet (acquisition flow of thereference clock information) will be described with reference to FIG.10. FIG. 10 is a diagram illustrating the acquisition flow of thereference clock information performed by reception apparatus 20 when thereference clock information is stored in the TLV packet.

In the flow of FIG. 10, first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S121), and extracts the TLV packetfrom the transfer slot (S122).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S123),and determines whether the data type is the reference clock information(S124). When the data type is the reference clock (Yes in S124),reference clock information extractor 15 extracts the reference clockinformation from the data field of the TLV packet (S125). Then,reference clock generator 16 generates the system clock based on thereference clock information (S126). On the other hand, when the datatype is not the reference clock information, (No in S124), theacquisition flow of the reference clock information ends.

In addition, in an unillustrated flow, IP demultiplexer 13 extracts theIP packet according to the data type. Then, the IP DEMUX process and MMTDEMUX process are performed on the extracted IP packet, and the MMTpacket is extracted. Furthermore, synchronizer 17 outputs video data todecoding presenter 18 with timing with which the time stamp of the videodata contained in the extracted MMT packet coincides with the referenceclock generated in step S126. Decoding presenter 18 decodes and presentsthe video data.

In a transmission method described above, the data type of the TLVpacket indicates that the reference clock information is stored, and thereference clock information is stored in the data field of the TLVpacket. By the transmission apparatus storing and transmitting thereference clock information by using a lower layer or lower protocolthan the MMT layer, reception apparatus 20 may reduce the processes andtime until the reference clock information is extracted.

Also, since reception apparatus 20 may extract and reproduce thereference clock information in a lower layer extending over the IPlayer, reception apparatus 20 may extract the reference clockinformation by hardware implementation. This allows reception apparatus20 to reduce more influence of jitter or the like than extracting thereference clock information by software implementation, and to generatehigher-precision reference clock.

Next, other methods for storing the reference clock information will bedescribed.

When the data length is uniquely determined according to the data typein the aforementioned flow of FIG. 10, the data length field does notneed to be transmitted. Here, when the data length field is nottransmitted, an identifier is stored indicating that the data lengthfield is data that is not transmitted.

Although the reference clock information is stored in the data field ofthe TLV packet according to the description of FIG. 10, the referenceclock information may be appended immediately before or after the TLVpacket. Also, the reference clock information may be appendedimmediately before or after data to be stored in the TLV packet. Inthese cases, a data type that allows specification of a position wherethe reference clock information is appended is added.

For example, FIG. 11 is a diagram illustrating structure in which thereference clock information is appended immediately before the IP packetheader. In this case, the data type indicates an IP packet withreference clock information. When the data type indicates an IP packetwith reference clock information, reception apparatus 20 (referenceclock information extractor 15) may acquire the reference clockinformation by extracting bits of a previously prescribed predeterminedlength of the reference clock information from a head of the data fieldof the TLV packet.

At this time, the data length may specify the length of data thatincludes the length of the reference clock information, and may specifythe length that does not include the length of the reference clockinformation. When the data length specifies the length of data thatincludes the length of the reference clock information, receptionapparatus 20 (reference clock information extractor 15) acquires data ofa length obtained by subtracting the length of the reference clockinformation from the data length from immediately after the referenceclock information.

When the data length specifies the length of data that does not includethe length of the reference clock information, reception apparatus 20(reference clock information extractor 15) acquires data of the lengthspecified by the data length from immediately after the reference clockinformation.

In addition, FIG. 12 is a diagram illustrating structure in which thereference clock information is appended immediately before the TLVpacket. In this case, the data type is a conventional data type. Anidentifier indicating that the TLV packet is a TLV packet with referenceclock information is stored, for example, in a slot header of thetransfer slot or the TMCC control information. FIG. 13 is a diagramillustrating structure of the transfer slot, and FIG. 14 is a diagramillustrating structure of the slot header of the transfer slot.

In FIG. 13, the transfer slot includes a plurality of slots (120 slotsof Slot #1 to Slot #120 in the example of FIG. 13). A bit numbercontained in each slot is a fixed bit number uniquely determined basedon a coding rate of error correction, and each slot has a slot headerand stores one or more TLV packets. Note that, in FIG. 13, the TLVpacket is variable-length.

In FIG. 14, a position of a head byte of a first TLV packet within theslot is stored in a head TLV instruction field (16 bits) of the slotheader as a value represented with a byte number from a slot head exceptthe slot header. Remaining 160 bits of the slot header is undefined.

The transfer slot includes 120 slots per frame as described above, and amodulation scheme is assigned to the slots in 5-slot unit. In addition,up to 16 streams may be transferred within one frame.

Note that the plurality of streams included in one transfer slot differfrom one another, for example, in content (or a company that providesthe content) transferred by the stream. In addition, each streamincludes one or more slots, and one slot does not extend over theplurality of streams.

When the identifier indicating that the TLV packet is a TLV packet withreference clock information is stored in the slot header, for example,information that allows specification of a position of the TLV packetwith reference clock information, kind of the reference clockinformation, data length, and the like are stored in the slot byextending (using) an undefined field of the slot header.

Note that all pieces of information including the information thatallows specification of the position of the TLV packet with referenceclock information, kind of the reference clock information, and datalength do no need to be stored in the slot header. The slot may indicateinformation that allows specification of and reference to the TLV packetwith reference clock information.

For example, when definition is made that the reference clockinformation is a 64-bit long-format NTP, that only one TLV packet withreference clock information may be stored in one slot, and that the oneTLV packet with reference clock information is always the head TLVpacket, a flag may be stored in the undefined area of the slot header.FIG. 15 is a diagram illustrating an example in which the flag is storedin the undefined area of the slot header.

In FIG. 15, the flag (described as “F” in the diagram) indicatingwhether the reference clock information is contained in the slot isstored in the undefined area of the slot header. With such a flag,reception apparatus 20 may determine that the head TLV packet is a TLVpacket with reference clock information.

In addition, the identifier (information) indicating that the TLV packetis a TLV packet with reference clock information may be stored in theTMCC control information. FIG. 16 is a diagram illustrating structure ofthe TMCC control information under a transfer scheme of an advancedbroadband satellite digital broadcast.

The information for specifying and referencing the TLV packet withreference clock information may be stored in extension informationwithin the TMCC control information illustrated in FIG. 16, and may bestored in another place within the TMCC control information. Forexample, stream classification/relative stream information in the TMCCcontrol information may be used as information for specifying andreferencing the TLV packet with reference clock information. FIG. 17 isa diagram illustrating the stream classification/relative streaminformation in the TMCC control information.

In FIG. 17, in the stream classification/relative stream information,the stream classification of each of 16 streams is indicated in 8 bits.That is, 1-frame transfer slot may transfer up to 16 (16-classification)streams. For example, the stream classification of an MPEG2-TS stream is“00000000”, and the stream classification of the TLV stream is“00000010”. However, under the current circumstances, theclassifications of other streams are unassigned or undefined.

Therefore, when the stream classification of the TLV stream withreference clock is defined, for example, as “00000100” and the relativestream is the TLV stream with reference clock, “00000100” is stored inthe stream classification/relative stream information in the TMCCcontrol information. Here, in the stream with the stream classificationof “00000100”, the TLV packet containing reference clock information isstored, for example, once per 5-slot unit which is a slot assignmentunit, or once per frame unit in stream classification/relative streaminformation 128.

Reception apparatus 20 analyzes stream classification/relative streaminformation 128 in the TMCC control information. When the streamclassification is “00000100”, reception apparatus 20 acquires the TLVpacket with reference clock from the slot determined in advance.

Note that a case may be considered where the stream classificationincluding download type TLV packets and the stream classificationincluding stream type TLV packets, such as video and audio, are defined.In such a case, reception apparatus 20 may determine that the referenceclock information is contained in the stream when the streamclassification of the received stream is a stream type TLV packet. Thisis because the reference clock information is not used in reproductionof download type TLV packets.

In addition, when the information for specifying and referencing the TLVpacket with reference clock information is stored in the extensioninformation of the TMCC control information, for example, informationfor each of 16 relative streams is stored in the extension area of theTMCC control information.

Also, as illustrated in FIG. 18, an area into which the reference clockinformation is stored may be newly defined in the undefined field of theslot header. FIG. 18 is a diagram illustrating an example in which thereference clock information is stored in the undefined field of the slotheader.

Also, the reference clock information may be stored in a previouslydetermined slot, and information indicating that the reference clockinformation is contained may be stored within the slot header. Here, thepreviously determined slot is, for example, a head slot of the transferslot (Slot #1 in the example of FIG. 13), and the reference clockinformation stored in the IP packet may be contained in the head TLVpacket within this slot. Also, when the plurality of streams arecontained in the transfer slot, the previously determined slot may be,for example, a head slot of each stream contained in the transfer slot,and the reference clock information stored in the IP packet may becontained in the head TLV packet within this slot.

Also, the TMCC control information may store information for specifyingand referencing the slot header containing the reference clockinformation. Note that a storage method of the information forspecifying and referencing the slot header containing the referenceclock information in the TMCC control information is similar to theaforementioned storage method of the information for specifying andreferencing the TLV packet with reference clock information, and thusdescription thereof will be omitted.

In this case, reception apparatus 20 analyzes the TMCC control signal,and when determination is made that the reference clock information isin the slot header, reception apparatus 20 extracts the reference clockinformation from the slot header.

Also, the TMCC control information may store the information indicatingthat the reference clock information is contained. FIG. 19 is a blockdiagram illustrating the functional configuration of reception apparatus20 when the information indicating that the reference clock informationis contained within the slot header is stored in the TMCC controlinformation. FIG. 20 is a diagram illustrating the acquisition flow ofthe reference clock information when the information indicating that thereference clock information is contained in the slot header is stored inthe TMCC control information.

In FIG. 19, when the information indicating that the reference clockinformation is contained within the slot header is stored in the TMCCcontrol information, in reception apparatus 20, reference clockinformation extractor 15 acquires the reference clock signal from thetransfer slot that is output from decoder 11.

In the flow of FIG. 20, decoder 11 decodes the transfer channel codeddata (S131), analyzes the TMCC control signal (S132), and determineswhether the reference clock information is in the slot header within thetransfer slot (S133). When the reference clock information is in theslot header (Yes in S133), reference clock information extractor 15extracts the reference clock information from the slot header (S134),and reference clock generator 16 generates the reference clock of thesystem (system clock) based on the reference clock information (S135).On the other hand, when the reference clock information is not in theslot header (No in S133), the acquisition flow of the reference clockinformation ends.

Such reception apparatus 20, which may acquire the reference clockinformation in the layer of the transfer slot, may acquire the referenceclock information more quickly than a case where the reference clockinformation is stored in the TLV packet.

As described above, by storing the reference clock information in theTLV packet or transfer slot, reception apparatus 20 may reduce theprocesses until the acquisition of the reference clock information, andmay shorten acquisition time of the reference clock information.

In addition, by storing the reference clock information in a physicallayer, reception apparatus 20 may easily implement acquisition andreproduction of the reference clock information by hardware, and mayreproduce a clock with higher-precision than acquisition andreproduction of the reference clock information by software.

In addition, in the aforementioned transmission method according to thefirst exemplary embodiment, the transmission apparatus adds, in thesystem in which the plurality of layers (protocols) exists including theIP layer, the time stamp of a medium based on the reference clockinformation in the layers upper than the IP layer, and transmits thereference clock information in the layers lower than the IP layer. Thisallows reception apparatus 20 to process the reference clock informationeasily by hardware.

Note that, based on a similar idea, storing the reference clockinformation within the IP packet in a condition of not being stored inthe MMT packet may also be considered. Even in such a case, receptionapparatus 20 may reduce the processes for acquiring the reference clockinformation as compared with the case where the reference clockinformation is stored in the MMT packet.

[Transmission Cycle of the Reference Clock Information]

Hereinafter, a transmission cycle of the reference clock informationwill be supplemented.

In the case of storing the reference clock information in the TLVpacket, for example, the transmission apparatus stores time when thehead bit of the TLV packet is transmitted as the reference clockinformation. In addition, not the transmission time of the head bit butpredetermined time determined differently may be stored as the referenceclock information.

The TLV packet containing the reference clock information is transmittedat predetermined intervals. In other words, the TLV packet containingthe reference clock information is contained in the transfer slot and istransmitted in a predetermined transmission cycle. For example, at leastone or more pieces of reference clock information in 100 ms may bestored in the TLV packet and be transferred.

In addition, the transmission apparatus may place the TLV packetcontaining the reference clock information at predetermined intervals ata predetermined position of the transfer slot under the advanced BStransfer scheme. In addition, the transmission apparatus may store theTLV packet containing the reference clock information once every 5-slotunit which is a slot assignment unit of the TLV packet, and may storethe reference clock information in the head TLV packet of the first slotof the 5-slot unit. That is, the transmission apparatus may place theTLV packet containing the reference clock information at a head withinthe head slot within the transfer slot (that is, immediately after theslot header).

Also, the transmission apparatus may place the TLV packet containing thereference clock information at predetermined intervals at apredetermined place of the transfer slot under the transfer scheme ofthe advanced broadband satellite digital broadcast. For example, thetransmission apparatus may store the reference clock information in thehead TLV packet of the first slot once every 5-slot unit which is a slotassignment unit. That is, the TLV packet positioned at a head within thehead slot of each stream contained in the transfer slot may contain thereference clock information. Also, the reference clock information maybe stored in the first slot within the relative stream.

In addition, the transmission cycle and transmission interval of thereference clock information may be changed according to a modulationscheme or coding rate of the transfer channel coding scheme.

[Method for Acquiring the Reference Clock Information in the Upper LayerQuickly]

Next, a method will be described for shorten time to the acquisition ofthe reference clock information by reception apparatus 20 performingbatch DEMUX processing from the lower layer to the upper layer.

Here, a method will be described in which the transmission apparatusstores the reference clock information in the upper layer such as theMMT packet, and stores in the IP packet the MMT packet in which thereference clock information is stored. In the method described below, bydefining a protocol for storing in the TLV packet the IP packet in whichthe reference clock information is stored, the reception apparatus makesdirect reference of the MMT packet which is the upper layer from thelower layer such as the TLV packet, and acquires the reference clockinformation contained in the MMT packet without performance of normalDEMUX processing.

The transmission apparatus contains the reference clock information inthe aforementioned control information stored in the MMT packet. Thepreviously determined packet ID is added to the control informationcontaining the reference clock information. Then, the transmissionapparatus stores the MMT packet containing the reference clockinformation in a dedicated IP data flow, and adds the previouslydetermined source IP address, destination IP address, source portnumber, destination port number, and protocol classification.

On receipt of the transfer channel coded data generated in this way,reception apparatus 20 may extract the IP packet containing thereference clock information by TLV demultiplexer 12 acquiring thepreviously determined IP data flow.

Note that when the IP packet undergoes header compression processing,reception apparatus 20 adds, for example, an identifier indicating thatthe IP packet contains the reference clock information to a contextidentifier indicating identical IP data flows. The context identifier isstored in a compressed IP packet header. In this case, receptionapparatus 20 may extract the IP packet containing the reference clockinformation with reference to the context identifier in the compressedIP packet header.

In addition, the IP packet containing the reference clock informationmay be prescribed not to undergo the header compression, and may beprescribed to always undergo the header compression. It may beprescribed that the previously determined context identifier may beadded to the IP packet containing the reference clock information, andthat all the headers are compressed.

In addition, a method may also be considered for defining, in a TLV datatype field, an identifier indicating that the TLV packet is an IP packetthat belongs to the IP data flow containing the reference clockinformation, or an identifier indicating that the TLV packet is acompressed IP packet that belongs to the IP data flow containing thereference clock information. The following describes the method.

Reception apparatus 20 determines the TLV data type. On determinationthat the reference clock information is contained, reception apparatus20 acquires the reference clock information contained within the MMTpacket directly from the IP packet.

Thus, reception apparatus 20 may extract the reference clock informationcontained in the MMT packet by extracting a bit string at a specificposition from the IP packet or compressed IP packet, without analyzingthe IP address, port number, or context identifier. Extracting the bitstring at a specific position means, for example, extracting informationof a specific length from a position that is offset by fixed-lengthbytes from the TLV packet header. Accordingly, the reference clockinformation is acquired.

The offset length of the fixed-length bytes for extracting the referenceclock information is uniquely determined for each of the IP packet andthe compressed IP packet. Therefore, reception apparatus 20 may acquirethe reference clock information by extracting the information of thespecific length from the position that is offset by the fixed-lengthbytes after determining the TLV data type.

Note that the aforementioned method is one example, and receptionapparatus 20 may acquire the reference clock information in the upperlayer from the lower layer by defining another protocol or identifier.For example, an identifier indicating whether the IP packet contains thereference clock information may be stored in a field other than the TLVdata type field.

In addition, for example, reception apparatus 20 may extract referencetime information contained in the MMT packet by extracting the bitstring of a specific position from the IP packet or compressed IP packetwithout analyzing the IP address, the port number, or the contextidentifier. FIG. 21 is a diagram illustrating a flow for extracting thebit string of a specific position from the IP packet or compressed IPpacket. Note that the configuration of reception apparatus 20 is similarto the block diagram illustrated in FIG. 8.

In the flow of FIG. 21, first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S141), and extracts the TLV packetfrom the transfer channel slot (S142).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S143),and determines whether the data type is an IP containing reference clockinformation (S144). When the determination is made that the data type isnot an IP packet containing reference clock information (No in S144),the flow ends. When the determination is made that the data type is anIP packet containing reference clock information (Yes in S144), TLVdemultiplexer 12 determines whether the IP header is compressed (S145).

When the IP header is not compressed (No in S145), reference clockinformation extractor 15 acquires the reference clock informationcontained within the MMT packet at a position that is offset byfixed-length N bytes from the TLV header (S146). When the IP header iscompressed (Yes in S145), reference clock information extractor 15acquires the reference clock information contained within the MMT packetat a position that is offset by fixed-length M bytes from the TLV header(S147).

Finally, reference clock generator 16 generates the system clock basedon the reference clock information (S148).

Note that, since data structure of the IP packet header differsaccording to whether the IP packet is IPv4 or IPv6, the fixed-length Nbytes and M bytes have different values.

While the normal MMT packet containing audio, video, control signal, andthe like undergoes DEMUX processing in normal steps, the MMT packetcontaining the reference clock information undergoes batch DEMUXprocessing from the lower layer to the upper layer. This allows thereception apparatus to acquire the reference clock information in thelower layer even when the reference clock information is stored in theupper layer. That is, this allows the reception apparatus to reduce theprocesses for acquisition of the reference clock information, to shortentime to the acquisition of the reference clock information, and tofacilitate hardware implementation.

Other Exemplary Embodiments

Although the first exemplary embodiment has been described above, thepresent disclosure is not limited to the aforementioned exemplaryembodiment.

Although the aforementioned exemplary embodiment has described thestorage method of the reference clock information, a plurality of piecesof reference clock information may be transmitted in one or more layers.When the plurality of pieces of reference clock information istransmitted, reception apparatus 20 may select one piece of thereference clock information and use the selected reference clockinformation for generation of the reference clock (system clock), andmay use both pieces of the reference clock information to generate thereference clock. At this time, reception apparatus 20 may selecthigh-precision reference clock information, and may select referenceclock information that may be acquired more quickly.

Also, it is assumed that, for example, in addition to the 32-bitshort-format NTP contained in the conventional MMT packet header,higher-precision reference clock information is transmitted. In such acase, information is further transmitted from the transmission apparatusfor allowing reception apparatus 20 to use the high-precision referenceclock information to reproduce the 32-bit short-format NTP. Suchinformation is, for example, time information indicating a relativerelationship between clocks, and a configuration, etc. for transmittingthe information by using CRI_descriptor( ), etc. may be considered.

Note that, when reception apparatus 20 may reproduce the 32-bitshort-format NTP, the conventional NTP field contained in the MMT packetheader is unnecessary. Therefore, the transmission apparatus may storeanother piece of information in the NTP field, and may perform headercompression by reducing the NTP field. When header compression isperformed, the transmission apparatus transmits information indicatingthat the NTP field is reduced. When the NTP field is reduced, receptionapparatus 20 generates the reference clock by using another piece ofreference clock information, and reproduces the 32-bit short-format NTP.

In addition, when the MMT packet is transferred using a broadbandtransfer channel, a broadband reception apparatus may use the 32-bitshort-format NTP for QoS control, and may not use the reference clockinformation. Accordingly, the reference clock information does not needto be transmitted through the broadband transfer channel. In addition,when end-to-end delay of the broadband transfer channel is within acertain value, the broadband reception apparatus may use the referenceclock information for clock reproduction.

Note that although the aforementioned first exemplary embodiment hasdescribed the case where the MMT/IP/TLV scheme is used as an example,schemes other than the MMT scheme may be used as a multiplexing scheme.For example, the present disclosure may also be applied to an MPEG2-TSscheme, RTP scheme, or MPEG-DASH scheme.

In addition, methods for header compression of IP packets include RoHC(Robust Header Compression) and HCfB (Header Compression forBroadcasting).

Schemes for storing IP packets in broadcast include a GSE (GenericStream Encapsulation) scheme, IPoverTS scheme using ULE (UnidirectionalLight-weight. Encapsulation), and the like, in addition to the TLVscheme.

The present disclosure may be applied to a case where any of suchschemes is used. Application of the present disclosure allows receptionapparatus 20 to achieve shortening of time to the acquisition of thereference clock information and reduction in the processes, and toachieve high precision of the clock by hardware implementation.

In addition, the present disclosure may be implemented as a transmissionapparatus (transmission method) that transmits the transfer slot thatstores the reference clock information by the above method. Thefollowing supplements a configuration of such a transmission apparatus.FIG. 22 is a block diagram illustrating a functional configuration ofthe transmission apparatus. FIG. 23 is a diagram illustrating anoperation flow of the transmission apparatus.

As illustrated in FIG. 22, transmission apparatus 30 includes generator31 and transmitter 32. Note that each component of transmissionapparatus 30 is specifically implemented by a microcomputer, aprocessor, dedicated circuitry, or the like.

Transmission apparatus 30 is specifically a broadcasting server, and isan example of the aforementioned “transmission apparatus” in the firstexemplary embodiment.

Generator 31 generates, for example, the transfer slot that stores theplurality of slots that each store the one or more TLV packets that eachstore the IP packet (S151 of FIG. 23). The transfer slot contains theplurality of relative streams that each include one or more slots.

Generator 31 contains the reference clock information, such as the NTPindicating time for reproduction of content (for example, broadcastcontent such as video and audio) in reception apparatus 20, in the TLVpacket positioned at a head within the head slot of each relative streamcontained in the transfer slot. Specifically, generator 31 includes acoder that codes the broadcast content, MMT multiplexer, IP multiplexer,and TLV multiplexer. Here, the TLV packet is an example of a firsttransfer unit, the slot is an example of a second transfer unit, and thetransfer slot is an example of a transfer frame. The relative stream isan example of the stream.

Transmitter 32 transmits the transfer slot generated by generator 31(transfer channel coded data containing the transfer slot) throughbroadcast (S152 of FIG. 23).

As also described in the aforementioned first exemplary embodiment,transmission apparatus 30 contains the reference clock information inthe TLV packet positioned at a head of each relative stream within thetransfer slot to allow simplification of the processes by whichreception apparatus 20 acquires the reference clock information of eachof the plurality of streams. Therefore, this may shorten time untilreception apparatus 20 acquires the reference clock information.

Note that in the aforementioned exemplary embodiment, components mayeach include dedicated hardware or may be implemented through executionof a software program suitable for each component. The components may beeach implemented by a program execution unit, such as a CPU and aprocessor, reading and executing the software program recorded in arecording medium such as a hard disk and a semiconductor memory.

In addition, the components may be circuits. These circuits mayconstitute one circuit as a whole, and may be different circuits. Inaddition, each of these circuits may be a general-purpose circuit, andmay be a dedicated circuit.

For example, in each of the aforementioned exemplary embodiments,processes executed by a specific processor may be executed by anotherprocessor. In addition, order of the plurality of processes may bechanged, and the plurality of processes may be executed in parallel.

The reception apparatus (reception method) and transmission apparatus(transmission method) according to one or more aspects have beendescribed above based on the exemplary embodiment. However, the presentdisclosure is not limited to this exemplary embodiment. The presentexemplary embodiment to which various modifications conceivable by aperson skilled in the art are made, and aspects that are made bycombining elements of different exemplary embodiments may also be withinthe scope of the one or more aspects as long as such aspects do notdepart from the gist of the present disclosure.

The transmission method according to the present disclosure is useful asa transmission method capable of reducing the processes of the receptionapparatus for acquiring the reference clock information when the MMTscheme is applied to a broadcasting system.

1-8. (canceled)
 9. A transmission method comprising: coding videocontent; configuring one or more transfer units that each include thecoded video content; and transmitting the one or more transfer units asa transmission signal, the transmission signal including first controlinformation, second control information, and the one or more transferunits, wherein the first control information includes a transmissionparameter used for the second control information, and the secondcontrol information is provided for each of the one or more transferunits, wherein in at least one transfer unit among the one or moretransfer units, the second control information of the transfer unitcontains clock information used for reproduction of the video content,wherein information indicating that the clock information is containedwithin the second control information of the transfer unit is stored inthe first control information, and wherein the clock information istransmitted cyclically.
 10. A reception method comprising: receiving atransmission signal, the transmission signal including one or moretransfer units that each include coded video content, first controlinformation, and second control information; decoding the coded videocontent; and extracting clock information used for reproduction of thevideo content from at least one transfer unit among the one or moretransfer units, wherein the first control information includes atransmission parameter used for the second control information, thesecond control information being provided for each of the one or moretransfer units, wherein in the at least one transfer unit among the oneor more transfer units, the second control information of the transferunit contains the clock information used for reproduction of the videocontent, wherein information indicating that the clock information iscontained within the second control information of the transfer unit isstored in the first control information, and wherein the clockinformation is transmitted cyclically.
 11. A transmission devicecomprising: coding circuitry which, in operation, codes video content;configuration circuitry which, in operation, configures one or moretransfer units that each include the coded video content; andtransmission circuitry which, in operation, transmits the one or moretransfer units as a transmission signal, the transmission signalincluding first control information, second control information, and theone or more transfer units, wherein the first control informationincludes a transmission parameter used for the second controlinformation, and the second control information is provided for each ofthe one or more transfer units, wherein in at least one transfer unitamong the one or more transfer units, the second control information ofthe transfer unit contains clock information used for reproduction ofthe video content, wherein information indicating that the clockinformation is contained within the second control information of thetransfer unit is stored in the first control information, and whereinthe clock information is transmitted cyclically.
 12. A reception devicecomprising: reception circuitry which, in operation, receives atransmission signal, the transmission signal including one or moretransfer units that each include coded video content, first controlinformation, and second control information; decoding circuitry which,in operation, decodes the coded video content; and extraction circuitrywhich, in operation, extracts clock information used for reproduction ofthe video content from at least one transfer unit among the one or moretransfer units, wherein the first control information includes atransmission parameter used for the second control information, thesecond control information being provided for each of the one or moretransfer units, wherein in the at least one transfer unit among the oneor more transfer units, the second control information of the transferunit contains the clock information used for reproduction of the videocontent, wherein information indicating that the clock information iscontained within the second control information of the transfer unit isstored in the first control information, and wherein the clockinformation is transmitted cyclically.